This study was conducted to investigate the content of sulfur dioxide residues in medicinal herbs in Seoul in 2009. Sulfur dioxide in the samples were determined by Monnier-Williams's modified method. A total of 1,821 samples of 205 different types of herbs were collected from Kyung-Dong Herb markets and Oriental medicine hospitals in Seoul. Of these samples, 642 samples were domestic, and 1,179 samples were imported. Of the 1,821 samples, 61 (3.3%, 31 types) failed to meet the regulations for sulfur dioxide residues of KFDA in medicinal herbs. Among these 61 unsuitable samples, 17 (7 types) were domestic, and 44 samples (26 types) were imported. The content of sulfur dioxide in the domestic medicinal herbs ranged from 0 to 809 mg/kg, while those in imported medicinal herbs ranged from 0 to 4,481 mg/kg. Approximately 84.6% of the samples contained less than 10 mg/kg of sulfur dioxide and about 10.0% of samples contained more than 30 mg/kg of sulfur dioxide.